Camshaft Arrangement
Camshaft under-mounted valve mechanism: The camshaft is installed in the crankcase, directly meshed with the camshaft timing gear and the crankshaft timing gear, and is driven by the crankshaft. The valve train group includes all the above-mentioned parts and is the most widely used.
Camshaft mid-mounted valve train: The camshaft is located in the upper part of the cylinder block. In order to reduce the quality of the reciprocating motion of the valve transmission mechanism, for high-speed engines, the position of the camshaft can be moved to the upper part of the cylinder block, and the rocker arm can be directly driven by the camshaft through the tappet without the push rod. This form of valve train generally needs to add an intermediate gear (idler gear) in the middle because the centerline of the crankshaft and the camshaft is far away.